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Quantitative Research Designs

9. Quantitative Research Designs. Learning Objectives. Identify Criteria For Exploratory, Descriptive, And Explanatory Studies Define Experimental Research Differentiate Between Internal And External Validity In Experimental Designs Identify Six Threats To Internal Validity

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Quantitative Research Designs

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  1. 9 Quantitative Research Designs

  2. Learning Objectives • Identify Criteria For Exploratory, Descriptive, And Explanatory Studies • Define Experimental Research • Differentiate Between Internal And External Validity In Experimental Designs • Identify Six Threats To Internal Validity • Identify Three Threats To External Validity

  3. Learning Objectives Distinguish Among True Experimental, Quasi-Experimental, And Pre-Experimental Designs Describe Three True Experimental Designs Describe Two Quasi-experimental Designs Describe Two Pre-experimental Designs

  4. Learning Objectives Discuss Four Types Of Nonexperimental Research Designs Recognize Two Types Of Settings In Which Research Is Conducted Identify Factors That Influence The Choice Of Research Designs Critique The Design Section Of Quantitative Studies

  5. Learning Objective OneIdentify Criteria For Exploratory, Descriptive, And Explanatory Studies

  6. Exploratory Studies • Little known about phenomenon • Flexible data collection approach • Qualitative and quantitative • Hypotheses not appropriate

  7. Descriptive Studies • Phenomena described • Relationship between variables examined • More information about variable(s) • Test hypotheses

  8. Explanatory Studies • Explanations for relationships among phenomena • Rigorous • Experimental research • Control over research conditions • Manipulate one or more variables

  9. Learning Objective TwoDefine Experimental Research

  10. Experimental Research • Cause + effect • Manipulate and control independent variable • Measure dependent variable

  11. Problems With Experimental Research • Casual relationships difficult to establish • Avoid using word prove • Controls difficult to apply to human beings

  12. Learning Objective ThreeDifferentiate Between Internal And External Validity In Experimental Designs

  13. Internal Validity • Degree to which changes in effect can be attributed to cause • Threats • Other factors that influence dependent variable • Constitute rival explanations or competing hypotheses

  14. External Validity • Degree to which results can be generalized • Questions to ask • With what degree of confidence can findings be transferred to the entire population? • Will these findings hold true with other groups and in other times and places?

  15. Relationship Between Internal and External Validity • As control for internal increases, external decreases • As concern for external increases, internal may be affected • Need to find balance

  16. Learning Objective FourIdentify Six Threats To Internal Validity

  17. Six Threats to Internal Validity • Selection bias • History • Maturation • Testing • Instrumentation change • Mortality

  18. Selection Bias • Results due to subject differences • Not due to independent variable manipulation • Means to control • Random group assignment

  19. History • Event other than the experimental treatment occurs during the course of study. • Event influences dependent variable. • Means to control • Simultaneous control and comparison groups • Random assignment of subjects to groups

  20. Maturation • Changes occur within subjects during study. • Changes influence the study results. • Means to control • Simultaneous control and comparison groups

  21. Testing • Influence of pretest or baseline data knowledge on posttest score

  22. Instrumentation Change • Difference between pretest and posttest measurement • Caused by change in accuracy rather than experimental treatment • Means to control • Judge training sessions • Trial instrument runs to check for changes • Continue to check instrument accuracy

  23. Mortality • Subject does not complete study. • Attrition rate different between groups • Means to control • No research design to control • Establish strong researcher-participant relationship

  24. Learning Objective FiveIdentify Three Threats To External Validity

  25. Major Threats to External Validity • Hawthorne effect • Experimenter effect • Reactive effects of the pretest

  26. Hawthorne Effect • Participants’ responses influenced by knowing they are being observed • Means to control • Double-blind experiment

  27. Experimenter Effect • Experimental research • Researcher characteristics or behaviors influence subject behaviors. • Examples of influential characteristics • Facial expression • Clothing • Age • Gender • Body build

  28. Rosenthal Effect • Nonexperimental research • Interviewer characteristics or behaviors influence respondent’s answers.

  29. Reactive Effects of the Pretest • Subjects sensitized to experimental treatment because of pretest • Examples of pretests • Paper-and-pencil test • Knowledge of baseline data

  30. Difference Between Internal and External Pretest Threats • Internal threat: pretest or baseline data knowledge cause of posttest results • External threat: pretest or baseline data knowledge catalyst (indirect cause)

  31. Learning Objective SixDistinguish Among True Experimental, Quasi-Experimental, AndPre-Experimental Designs

  32. Experimental Research Designs • True experimental • Quasi-experimental • Pre-experimental

  33. True Experimental Design • Great deal of control • Internal validity threats minimized • Causality inferred with confidence

  34. True Experimental Design Criteria • Researcher manipulates the experimental variable(s). • One experimental group and one comparison group • Subjects randomly assigned to groups

  35. Quasi-Experimental Design • No comparison group • Subjects not randomly assigned to groups

  36. Advantages and Disadvantages of Quasi-Experimental Design • Advantages • Real world more closely approximated • Disadvantages • Not as much control as true experimental design

  37. Pre-Experimental Design • Considered weak • Researcher has little control.

  38. Learning Objective SevenDescribe Three True Experimental Designs

  39. Experimental Designs • Pretest-posttest control group design • Posttest-only design • Solomon four-group design

  40. The Pretest-PosttestControl Group Design • Most frequently used experimental design • Criteria • Subjects randomly assigned to groups • Pretest given to both groups • Experimental group receives experimental treatment. • Comparison group receives routine treatment or no treatment. • Posttest given to both groups

  41. The Pretest-PosttestControl Group Design (cont’d) • Advantages • Controls for all internal validity threats • Controls for initial differences by adjusting posttest scores statistically • Disadvantages • External threat of reactive effects of the pretest • Can only be generalized to situations in which pretest is administered

  42. The Posttest-OnlyControl Group Design • Subjects randomly assigned to groups • Experimental group receives the experimental treatment. • Comparison group receives routine treatment or no treatment. • Posttest given to both groups

  43. Advantages of Posttest-Only Control Group Design • Easier to carry out • Eliminates reactive effects of the pretest on the posttest

  44. The Solomon Four-Group Design • All subjects are randomly assigned to one of four groups. • Two groups—experimental group 1 and comparison group 1— pretested • Two groups—experimental group 1 and experimental group 2—receive experimental treatment. • Two groups—comparison group 1 and comparison group 2—receive routine treatment or no treatment.

  45. Solomon Four-Group Design • Posttest given to all four groups • Advantages • Minimizes threats to both internal and external validity • Differences between groups can be associated with the experimental treatment. • Disadvantages • Requires a large sample • Statistical analysis is complicated.

  46. Learning Objective EightDescribe Two Quasi-Experimental Designs

  47. Quasi-Experimental Designs • Nonequivalent control group design • Time-series design

  48. The NonequivalentControl Group Design • Similar to pretest-posttest control group design • No random assignment of subjects to groups

  49. Internal Validity in Nonequivalent Control Group Design • Threats to internal validity controlled • History • Testing • Maturation • Instrumentation change • Threats to internal validity that remain • Selection bias

  50. Time-Series Design • Periodic observations or measurements of subjects • Experimental treatment administered between two of the observations

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